Blackwell Publishing AsiaMelbourne, AustraliaWBMWeed Biology and Management1444-61622006 Weed Science Society of JapanDecember 200664235240Original ArticleInsect pollinators of Rosa multifloraL. C. Jesse
et al.
Weed Biology and Management 6, 235–240 (2006)
RESEARCH PAPER
Insect pollinators of the invasive plant, Rosa multiflora
(Rosaceae), in Iowa, USA
LAURA C. JESSE,1* KIRK A. MOLONEY2 and JOHN J. OBRYCKI3
Departments of Entomology and 2Ecology, Evolution and Organismal Biology, Iowa State University, Ames, IA and
3
Department of Entomology, University of Kentucky, Lexington, KY, USA
1
Invasive species often require mutualistic relationships to successfully invade new environments. Insect pollination is an example of a mutualism that is required for seed-set in the invasive species, Rosa multiflora Thunb. (Rosaceae), an obligate outcrosser. To determine the insect
pollinators visiting R. multiflora flowers in Iowa, USA, we collected insects on yellow sticky
traps placed on plants during the period of blooming and visually observed insects visiting
the flowers. The common insect orders that were collected on the sticky traps included
Coleoptera, Diptera, Hemiptera, Hymenoptera, Mecoptera, and Thysanoptera. Many of the
insects found on the sticky cards were known to feed on pollen. However, we did not collect
Apidae (bumble bees and honey bees) on the sticky cards. We observed Bombus spp. and Apis
mellifera foraging on the flowers. Syrphid flies were the most commonly observed taxa visiting
the flowers. Our results indicate that R. multiflora is utilizing common generalist insect pollinators in Iowa and that pollination is not a limiting factor for this invasive species.
Keywords: invasive species, mutualistic relationships, pollinators, Rosa multiflora.
INTRODUCTION
Research on the ecology of invasive plants has traditionally focused on how competitive interactions affect the
structure of a community and the ability of the invading
plant species to establish (Elton 1958; Levine & D’Antonio 1999; Callaway & Aschehoug 2000; Richardson
et al. 2000). Invading plants with no close relatives
within their new community are predicted to be more
successful as they avoid direct competition for resources
(Richardson et al. 2000). Alternatively, invaders might be
more able to co-opt the mutualistic relationships (e.g.
pollination) of native species that are close relatives
(Richardson et al. 2000).
When a species invades a new area it leaves behind associations that it has evolved within its native range (Parker
1997). This might be beneficial to the invading plant
*Correspondence to: Laura Jesse, Iowa State University, 104 Insectary, Ames, IA 50011, USA.
Email: ljesse@iastate.edu
Received 10 May 2006; accepted 15 July 2006
doi:10.1111/j.1445-6664.2006.00221.x
when herbivores that negatively affect its population
growth are left behind (Blossey & Notzold 1995; Keane
& Crawley 2002). However, coevolved mutualistic relationships are also severed, which could potentially limit
the population growth of an invading species (Parker
1997). Establishing mutualistic interactions with organisms already established in the new ecosystem might
greatly enhance the ability of the invader to establish and
spread (Simberloff & Von Holle 1999; Richardson et al.
2000).
Pollination is one mutualistic relationship that has been
studied for several invasive plant species (Parker 1997;
Grabas & Laverty 1999; Barthell et al. 2001; Brown &
Mitchell 2001; Chittka & Schurkens 2001; Larson et al.
2002; Parker & Haubensak 2002; Waites & Agren 2004;
Simpson et al. 2005; Morales & Aizen 2006). Many
highly successful alien plants are self-fertilizing (e.g. garlic mustard [Alliaria petiolata], cheatgrass [Bromus tectorum]), but there are many invaders that are obligate
out-crossers (e.g. purple loosestrife [Lythrum salicaria],
spotted knapweed [Centaurea maculosa], multiflora rose
[Rosa multiflora]). When a self-incompatible plant species
that is insect-pollinated is introduced in a new environ-
© 2006 The Authors
Journal compilation © 2006 Weed Science Society of Japan
236
L. C. Jesse et al.
Table 1. Description of the Iowa field sites used in this research that were infested with Rosa multiflora
Site
County
Dakins Lake
Story
Owner
CCB
Christainsen
Story
Forest Preserve
Redbird Farm
Johnson
CCB
Frytown
Johnson
CCB
Kent Park
Johnson
CCB
Boone Company
Boone
Private
Iowa DNR
Description
Heavily infested park, plants in unmowed grassy areas and under trees
adjacent to lake
Moderate infestations in northern half of park in unmowed areas and in forest
understory with plants, especially along the southern forest edge
Grassy slopes of heavily infested farm. Management with herbicides and
mowing on parts of the infestation
Study site in infestation in an open sunny area that appeared to have been
planted with rows of shrubs
Study site east of Conservation Education Center in a ravine surrounded by
trees, but mainly open and sunny
Heavily infested, active cattle pasture. Plants in open sunny areas and
underneath trees
CCB, County Conservation Board; DNR, Department of Natural Resources.
ment, its pollinators must be introduced with the plant
or the plant must attract insect species as pollinators to
successfully reproduce (Parker 1997; Simberloff & Von
Holle 1999). Pollinators might also be a factor in determining the rate of spread of invasive plants that do not
spread clonally (Parker & Haubensak 2002).
Rosa multiflora Thunb. (Rosaceae) currently infests
45 million acres (18.2 million ha) in the eastern half of
the USA, reducing the value of land for grazing or
recreational purposes because dense patches of the
plant are impassable and are not utilized by most livestock (Loux et al. 2005). Rosa multiflora has been
declared a noxious weed in nine states, including Iowa
(Amrine & Stasny 1993). Rosa multiflora is a vigorous
shrub with long, arching branches that can grow to a
height and width of 2.5 m (Steavenson 1946). It produces numerous panicles, with ≤ 200 flowers on a
single panicle (loosely branched cluster of flowers)
(Steavenson 1946). Each flower produces a single hip
(fruit); the fleshy hips are red and remain on the plant
throughout the winter. A mature healthy plant can
produce up to 500 000 seeds annually (Amrine 2002).
We are not aware of any published data on the pollinators of R. multiflora in North America; however, European honey bees, Apis mellifera (Hymenoptera: Apidae),
bumble bees, Bombus spp. (Hymenoptera: Apidae), and
syrphid flies (Diptera: Syrphidae) have been observed
visiting R. multiflora flowers on other continents. For
example, Bombus spp., A. mellifera, and the syrphid fly,
Syrphus ribesii, visited R. multiflora flowers in the Netherlands (Stougaard 1983). Presumably, these insects are
involved in the natural pollination of R. multiflora in
Europe. In Korea, part of the home range of
R. multiflora, A. mellifera was the major pollinator of
R. multiflora (Lee et al. 1995).
The objectives of this study were to: (i) determine which
insect taxa associate with R. multiflora during bloom and
which insect taxa are observed visiting R. multiflora flowers; and (ii) calculate the visitation rates of common
insect pollinators (i.e. Apis spp. and Bombus spp.).
MATERIALS AND METHODS
Sticky card samples
In 2002, yellow sticky cards (28 cm × 22.8 cm, Pherocon AM; Trece, Adair, OK, USA) were used to sample
the insects occurring on R. multiflora plants during
flowering (late-May to mid-June in Iowa). The sticky
cards were set up at three sites in eastern Iowa
(Johnson County) on 25 and 26 May and at two sites
in central Iowa (Story County) on 29 May, when
R. multiflora had buds but was not yet flowering.
Table 1 describes the sites. At each site, the cards were
placed on five R. multiflora plants growing ≈ 4 m apart
and were replaced weekly for 3 weeks, for a total of 15
sticky cards per site. Each card was folded open around
the middle of a branch and the ends were secured to
each other with staples or binder clips. The branches
used all had flower buds and were ≈ 1.5 m above the
ground.
In 2003, sticky cards were placed on three plants at each
of four sites (Table 1). As in 2002, the cards were
replaced weekly for 3 weeks (a total of 36 sticky cards).
Two sites were located in Jackson County and two sites
© 2006 The Authors
Journal compilation © 2006 Weed Science Society of Japan
Insect pollinators of Rosa multiflora
were located in Allamakee County in north-eastern
Iowa; all sites were pasture areas.
Each sticky card collected in 2002 and 2003 was divided
into 63 (2.54 cm × 2.54 cm) squares. Ten squares were
randomly selected on each card and the insects in those
squares were identified to order and, if possible, to family. The number of insects on the 10 squares was used to
estimate the number of insects on the entire card. The
results are presented as the average number of insects per
card for the entire sampling period.
Field observations
For 3 years, 2002–2004, direct observations were made
of flowering R. multiflora to determine which insects
were visiting the flowers. In 2002, observations and collections of visitors were conducted in early June at two
sites in Story County in central Iowa and two sites in
Johnson County in eastern Iowa (Table 1). Four plants at
each site were observed for 10 min each between
10.00 h and 14.00 h.
In 2003 and 2004, observations of the pollinators were
conducted at three sites infested with R. multiflora in
central Iowa (Christiansen and Dakins Park in Story
County and a pasture in Boone County; Table 1).
We defined a pollinator as an insect that was on a
R. multiflora flower and appeared to be actively consuming or collecting pollen. At each site, three R. multiflora
growing in full sun were selected for the observations.
Two branches on each plant were observed for 10 min
each. The observations were conducted between
10.00 h and 15.00 h.
In 2003, observations were conducted at Christiansen
Park on 4 and 10 June, Dakins Park on 7, 12, and 16
June, and at the Boone County site on 5, 10, and 13
June. In 2004, observations were conducted at Christiansen Park on 28 and 31 May, Dakins Park on 31 May,
and 6 and 8 June, and at the Boone County site on 29
May, and 5 and 7 June. In 2003, when a honey bee or
bumble bee was observed on a R. multiflora plant, the
number of flowers visited on the plant was recorded to
determine the visitation rate (number of flowers visited
per min).
RESULTS
In 2002 and 2003, we collected Insecta, Acari, Arachnida, and Opiliones on sticky cards on R. multiflora
bushes during flowering. Insecta was the most common
taxon, represented by 11 orders and 48 families in 2002
and nine orders and 33 families in 2003 (Fig. 1). We
237
report only the groups that had at least three individuals
captured during the entire sampling period (Fig. 1).
We collected many species of Diptera, Coleoptera,
Hymenoptera, and other arthropod orders that could
not be identified to family. We did not catch any Apidae
on the sticky cards, possibly because they avoided the
cards or were able to pull loose from the cards. Many of
the insect families captured by the sticky cards are
known to feed on pollen and might serve to move pollen
between flowers. There were fewer insect families collected on the sticky cards in 2003 (Fig. 1). This could be
related to differences in sampling (fewer field sites in
2003) or to differences in the field sites: in 2002, we
sampled R. multiflora growing in park areas and, in 2003,
we sampled R. multiflora growing in pastures.
Very few insect pollinators were observed visiting
R. multiflora flowers in 2002. Insects were observed on
the flowers of two of four plants at Christiansen, four of
four plants at Dakins, one of four plants at Kent, three of
four plants at Frytown, and one of four plants at Redbird. Apis mellifera and Bombus spp. were observed, but
were not common. Sryphid flies were the most commonly observed insects visiting flowers. The insects collected from the flowers included Syrphidae, Formicidae,
Chrysopidae, Cantheridae, Miridae, and Bombyliidae.
In 2003, 99 individual insects were observed visiting
R. multiflora flowers. Syrphidae were the most common
pollinators, comprising 43% of the insects observed
(Fig. 2). Other dipteran species were the second largest
group (35%), which consisted primarily of calypterate
muscoid flies. Apis mellifera, Bombus spp., and solitary
bees made up 21% of the observed pollinators.
In 2003, we counted the number of flowers visited by
A. mellifera and Bombus spp. Fourteen A. mellifera were
observed at Christiansen Park (on 4 June) and the Boone
County site (5 and 13 June). The A. mellifera had a foraging rate of 9.7 ± 0.6 flowers min−1. Five Bombus spp.
were observed at Christiansen Park on 4 June. The Bombus spp. foraged at a rate of 15.6 ± 3.4 flowers min−1.
In 2004, we observed 106 insects visiting R. multiflora
flowers. Syrphids made up almost half of the insects
observed (Fig. 2). Apis mellifera and Diptera (primarily
calypterate muscoid flies) were the second most common flower visitors. We observed 12 Coleoptera visiting
flowers; most were Cantharidae and Staphylinidae.
DISCUSSION
Our results indicate that similar species of pollinating
insects visit R. multiflora in Iowa compared to other con-
© 2006 The Authors
Journal compilation © 2006 Weed Science Society of Japan
L. C. Jesse et al.
238
Insect taxa
(a)
Dolichopodidae
Calyptratae
Mycetophilidae
Cecidomyiidae
Phoridae
Rhagionidae
Calliphoridae
Psychodidae
Tephritidae
Empididae
Sepsidae
Pipunculidae
Chalcidoidea
Ichneumonidae
Braconidae
Chrysididae
Formicidae
Vespidae
Staphylinidae
Mordellidae
Cantharidae
Chrysomelidae
Curculionidae
Coccinellidae
Lampyridae
Buprestidae
Panorpidae
Thysanoptera
Cicadellidae
Aphididae
Membracidae
Fulgoridae
Anthocoridae
0
10
20
30
40
50
60
70
80
90
100
Insect taxa
(b)
Dolichopodidae
Calyptratae
Rhagionidae
Psychodidae
Cecidomyiidae
Syrphidae
Mycetophilidae
Sepsidae
Phoridae
Tephritidae
Calliphoridae
Chalcidoidea
Ichneumonidae
Chrysididae
Mordellidae
Lampyridae
Cantharidae
Panorpidae
Thysanoptera
Cicadellidae
Fulgoridae
Aphididae
Membracidae
0
10
20
30
40
50
60
70
80
Number of insects
tinents (Stougaard 1983; Lee et al. 1995). The two most
common pollinators we observed visiting flowers were
Syrphidae (hover flies) and A. mellifera, followed by other
species of flies. Bombus spp., solitary bees, and Coleoptera
also were observed visiting flowers. In the Netherlands,
Stougaard (1983) observed Bombus spp., A. mellifera, and
Syrphidae and, in Korea, A. mellifera was the major pollinator of R. multiflora, while Diptera and Coleoptera also
were observed visiting flowers (Lee et al. 1995).
In addition to the insects observed visiting flowers, a
wide variety of insects were captured on the sticky cards
placed on the flowering R. multiflora branches. Calyptratae (Diptera), thrips (Thysanoptera), and Chalcidoidea (Hymenoptera) were common insects trapped on
90
100
Fig. 1. The average number of
insects per sticky card in (a) 2002 (75
sticky cards) and (b) 2003 (36 cards).
The number of insects on the total
card was estimated from a subsample
of 10 of 63 squares. (), insect groups
that are known to serve as pollinators
or eat pollen; ( ), insect groups that
are not known to serve as pollinators
or eat pollen.
the sticky cards. These insects are known to feed on pollen and could serve as pollinators of R. multiflora. Some
of the other insects found on the sticky cards were probably feeding on R. multiflora leaves: Cicadellidae
(Hemiptera), Aphididae (Hemiptera), Membracidae
(Hemiptera), and Fulgoridae (Hemiptera). Other insects
captured on the sticky cards might have been attracted
by the dead insects (Panorpidae) or are very common in
the habitats where R. multiflora grows (Dolichopodidae,
Cecidomyidae, Phoridae, Rhagionidae).
For some invasive plants, the rate of spread can be limited by a lack of pollinator visits (Parker 1997; Larson
et al. 2002; Parker & Haubensak 2002). For example,
Scotch broom (Cytisus scoparius), French broom (Genista
© 2006 The Authors
Journal compilation © 2006 Weed Science Society of Japan
Insect pollinators of Rosa multiflora
(a)
239
(b)
Other
Hymenoptera
1%
Other Hymenoptera
3%
Solitary bee
2%
Halictidae
4%
Bumble bee
5%
Coleoptera
11%
Honey bee
14%
Syrphidae
43%
Solitary bee
10%
Syrphidae
48%
Other Diptera
12%
Honey bee
12%
Other Diptera
35%
Fig. 2. The relative abundance of insects visiting Rosa multiflora flowers at three sites in central Iowa over eight sampling
dates in late May or early June in (a) 2003 and (b) 2004.
monspessulana), and Japanese honeysuckle (Lonicera japonica) are three invasive plants that require insect pollinators
and have been found to have low seed-set related to a
lack of insect pollinators (Parker 1997; Larson et al.
2002; Parker & Haubensak 2002). Although these plants
are currently spreading, it seems likely that the lack of
pollinators is reducing the rate of invasion in at least part
of their range (Parker 1997; Parker & Haubensak 2002).
Our study did not examine the effects of pollinators on
the output of viable seeds by R. multiflora. However, we
have observed low numbers of viable seeds in dissected
rosehips ( Jesse 2006). It is possible that an increase in
insect visitation rates could increase the seed output of
R. multiflora.
Our results are similar to previous studies examining the
pollinators of invasive weeds. For example, in Washington, the primary pollinators of the invasive shrub, C. scoparius, were Bombus spp. and A. mellifera (Parker 1997).
Apis mellifera appears to play an important role in pollinating invasive plants, although it was not the most common insect observed. Apis mellifera comprised 14% of the
observed pollinators of R. multiflora in 2003 and 12% in
2004. In other studies, A. mellifera was observed pollinating C. scoparius and G. monspessulana (Parker &
Haubensak 2002) and was the most common pollinator
of L. salicaria (Grabas & Laverty 1999) and yellow starthistle, Centaurea solstitalis (Barthell et al. 2001). It is not
surprising that a generalist pollinator like A. mellifera,
which has been introduced around the world for apicul-
ture and the pollination of fruit trees, is also serving as a
pollinator for introduced plants.
Invasive plants with showy flowers or high nectar reward
might out-compete native plants for pollinators. Chittka
and Schurkens (2001) found a reduction in pollinators
and a corresponding reduction in seed-set by the native
Stachys palustris when grown with the invasive Indian
balsam, Impatiens glandulifera. Purple loosestrife reduced
seed-set in nearby native plants (Eupatorium maculatum,
Eupatorium perfoliatum, Impatiens capensis) by pollen contamination or by directly competing for pollinators
(Grabas & Laverty 1999). Similarly, Brown et al. (2002)
found reduced seed-set in the native Lythrum alatum
when grown with L. salicaria. Future research is needed
to determine if R. multiflora could be reducing the pollination of native roses or other species blooming during
the same time period.
In summary, it appears that there is a variety of insects
in Iowa that serves as pollinators of R. multiflora. We
observed frequent visits to R. multiflora flowers by syrphid flies, A. mellifera, and Bombus spp. More research is
needed to determine if a low rate of pollination could be
the cause of the low number of viable seeds observed in
dissected R. multiflora hips.
ACKNOWLEDGMENTS
We would like to thank the Story County Conservation
Board for letting us conduct this survey in their parks.
© 2006 The Authors
Journal compilation © 2006 Weed Science Society of Japan
240
L. C. Jesse et al.
This research was partially funded by a grant from the
College of Agriculture at Iowa State University. This is a
Journal Paper of the Iowa Agriculture and Home Economics Experiment Station, Ames, Iowa, Project No.
6628, supported by the Hatch Act and State of Iowa
funds.
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© 2006 The Authors
Journal compilation © 2006 Weed Science Society of Japan